Triboelectric generator

ABSTRACT

A triboelectric generator includes first and second electrodes spaced apart from each other, a first charging object on a surface of the first electrode facing the second electrode, a second charging object provided between the first charging object and the second electrode, and a grounding unit configured to intermittently interconnect the second charging object and a charge reservoir due to motion of the second charging object. The first charging object is configured to be positively charged due to contact. The second charging object is configured to be negatively charged due to contact.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119 to Korean PatentApplication No. 10-2016-0057136, filed on May 10, 2016, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein in its entirety by reference.

BACKGROUND 1. Field

The present disclosure relates to triboelectric generators, and moreparticularly, to triboelectric generators having grounding structures.

2. Description of Related Art

Energy harvesting technology is currently prominent all over the world.Energy harvesting devices are new environment-friendly energy generatingdevices configured to (or capable of) transforming mechanical energygenerated from wind or vibration in nature, motion of people, or thelike into electrical energy.

A triboelectric generator is an energy harvesting device for generatingelectrical energy by using charge transfer occurring due to frictionbetween two charging objects. The triboelectric generator has a highenergy transformation efficiency and thus may have a high output byusing a small external force. In addition, the triboelectric generatordoes not have temporal and spatial restrictions compared to energyharvesting devices using heat or sunlight, and may continuously generateelectrical energy compared to energy harvesting devices that use apiezoelectric material to generate electrical energy based ontransformation of the piezoelectric material.

SUMMARY

Provided are triboelectric generators having grounding structures.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of example embodiments.

According to some example embodiments of inventive concepts, atriboelectric generator includes first and second electrodes spacedapart from each other, a first charging object and a second chargingobject, and a grounding unit. The first charging object may be on asurface of the first electrode facing the second electrode and may beconfigured to be positively charged due to contact with a secondcharging object. The second charging object may be between the firstcharging object and the second electrode and the second charging objectmay be configured to be negatively charged due to contact with the firstcharging object. The grounding unit may be configured to intermittentlyinterconnect the second charging object and a charge reservoir due tomotion of the second charging object.

In example embodiments, the first charging object may contact thesurface of the first electrode, and the second charging object may bespaced apart from the first charging object and the second electrode.

In example embodiments, the first and second charging objects may beconfigured to contact each other in response to a first force beingapplied to one of the first and second electrodes, and the secondcharging object and the second electrode may be configured to contacteach other in response to a second force being applied to one of thefirst and second electrodes.

In example embodiments, the second charging object may be electricallyconnected via the grounding unit to the charge reservoir in response tothe second charging object moving toward the second electrode.

In example embodiments, the triboelectric generator may further includefirst elastic supporters between the first and second charging objects,and second elastic supporters may be between the second charging objectand the second electrode.

In example embodiments, each of the first elastic supporters may have amodulus of elasticity less than a modulus of elasticity of each of thesecond elastic supporters.

In example embodiments, the first charging object may include at leastone of polyformaldehyde, ethylcellulose, polyamide, melamine formol,wool, silk, mica, and nylon.

In example embodiments, the second charging object may include aconductive material.

In example embodiments, the second charging object may include at leastone of aluminum (Al), copper (Cu), silver (Ag), gold (Au), and steel.

In example embodiments, at least one of the first and second chargingobjects may be doped with a dopant to control charge characteristicsthereof.

In example embodiments, at least one of a contact surface of the firstcharging object and a contact surface of the second charging object mayinclude a plurality of protrusions.

In example embodiments, each of the first and second electrodes mayinclude at least one of graphene, carbon nanotubes (CNT), indium tinoxide (ITO), metal, and conductive polymer.

In example embodiments, the first and second electrodes may be on firstand second substrates, respectively.

In example embodiments, each of the first and second substrates mayinclude one of a hard material and a flexible material.

In example embodiments, the grounding unit may include a conductivemember and an elastic member. The conductive member may be providedbetween the second charging object and the second electrode, and may beconfigured to intermittently contact the second charging object. Theelastic member may be configured to elastically support the conductivemember.

In example embodiments, the grounding unit may include a switchingdevice configured to intermittently interconnect the second chargingobject and the charge reservoir.

In example embodiments, the grounding unit may include a conductivemember and an insulating member. The conductive member may be configuredto electrically connect the second charging object and the chargereservoir to each other. The insulating member may be configured toinsulate the second charging object and the charge reservoir from eachother.

In example embodiments, the charge reservoir may include ground or aconductive member.

In example embodiments, the conductive member may include a metal film.

According to some example embodiments of inventive concepts, atriboelectric generator may include a first substrate and a secondsubstrate spaced apart from each other, a first electrode and a secondelectrode spaced apart from each other between the first substrate andthe second substrate, a first charging object and a second chargingobject between the first electrode and the second electrode, asupporting structure, and a grounding unit configured to intermittentlyconnect the second charging object and a charge reservoir due inresponse to motion of the second charging object towards the groundingunit. The first electrode may be connected to the first substrate. Thesecond electrode may be connected to the second substrate. The firstcharging object may be connected to the first electrode. The firstcharging object and the second charging object may face each other. Thefirst charging object and the second charging object may be configuredto be charged a first type and a second type, respectively, in responseto the first charging object and the second charging object contactingeach other. The first type may be opposite the second type.

In example embodiments, the first charging object may include at leastone of polyformaldehyde, ethylcellulose, polyamide, melamine formol,wool, silk, mica, and nylon. The second charging object may include atleast one of aluminum (Al), copper (Cu), silver (Ag), gold (Au), andsteel.

In example embodiments, the triboelectric generator may further includea supporting structure. The supporting structure may couple the secondcharging object to one of the first substrate, the first chargingobject, and the second substrate.

In example embodiments, the grounding unit may include a switchingdevice configured to intermittently interconnect the second chargingobject and the charge reservoir.

In example embodiments, the grounding unit may include a conductivemember and an insulating member. The conductive member may be configuredto electrically connect the second charging object and the chargereservoir to each other. The insulating member may be configured toinsulate the second charging object and the charge reservoir from eachother.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of example embodiments, takenin conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of a triboelectric generator according tosome example embodiments;

FIG. 2 is a cross-sectional view of the triboelectric generatorillustrated in FIG. 1;

FIGS. 3A to 3H are cross-sectional views for describing a first cycleoperating mechanism of the triboelectric generator illustrated in FIG.1;

FIGS. 4A to 4H are cross-sectional views for describing a second cycleoperating mechanism of the triboelectric generator illustrated in FIG.1;

FIG. 5 is a cross-sectional view of a modified example of a secondcharging object of the triboelectric generator illustrated in FIG. 1;

FIG. 6 is a cross-sectional view of a charge reservoir of atriboelectric generator modified from FIG. 1;

FIG. 7 is a cross-sectional view of a grounding unit of a triboelectricgenerator modified from FIG. 1;

FIG. 8 is a cross-sectional view of a grounding unit of a triboelectricgenerator modified from FIG. 1;

FIGS. 9A to 9C are cross-sectional views showing operation of thegrounding unit illustrated in FIG. 8;

FIG. 10 is a cross-sectional view of a triboelectric generator accordingto some example embodiments;

FIGS. 11A to 11H are cross-sectional views for describing a first cycleoperating mechanism of the triboelectric generator illustrated in FIG.10;

FIGS. 12A to 12H are cross-sectional views for describing a second cycleoperating mechanism of the triboelectric generator illustrated in FIG.10;

FIG. 13 is a perspective view of a triboelectric generator according tosome example embodiments;

FIGS. 14A to 14E are cross-sectional views showing operation of thetriboelectric generator illustrated in FIG. 13;

FIG. 15 is a cross-sectional view of a triboelectric generator accordingto some example embodiments;

FIGS. 16A to 16D are cross-sectional views showing operation of thetriboelectric generator illustrated in FIG. 15;

FIG. 17 is a cross-sectional view of a triboelectric generator accordingto some example embodiments;

FIGS. 18A to 18D are cross-sectional views showing operation of thetriboelectric generator illustrated in FIG. 17;

FIG. 19 is a cross-sectional view of a triboelectric generator accordingto some example embodiments;

FIGS. 20A to 20D are cross-sectional views showing operation of thetriboelectric generator illustrated in FIG. 19;

FIG. 21 is a cross-sectional view of a triboelectric generator accordingto some example embodiments;

FIGS. 22A to 22D are cross-sectional views showing operation of thetriboelectric generator illustrated in FIG. 21;

FIG. 23 is a cross-sectional view of a triboelectric generator accordingto some example embodiments;

FIGS. 24A to 24D are cross-sectional views showing operation of thetriboelectric generator illustrated in FIG. 23;

FIG. 25 is a cross-sectional view of a triboelectric generator accordingto some example embodiments; and

FIG. 26 is an illustration of a triboelectric system according to someexample embodiments.

DETAILED DESCRIPTION

Reference will now be made in detail to example embodiments illustratedin the accompanying drawings, wherein like reference numerals refer tolike elements throughout. In this regard, example embodiments should notbe construed as being limited to the descriptions set forth herein.Accordingly, the example embodiments are merely described below, byreferring to the figures, to explain aspects. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items. Expressions such as “at least one of,” whenpreceding a list of elements, modify the entire list of elements and donot modify the individual elements of the list.

FIG. 1 is a perspective view of a triboelectric generator 100 accordingto some example embodiments. FIG. 2 is a cross-sectional view of thetriboelectric generator 100 illustrated in FIG. 1.

Referring to FIGS. 1 and 2, the triboelectric generator 100 includesfirst and second electrodes 112 and 122, a first charging object 131provided on a surface of the first electrode 112, a second chargingobject 132 provided between the first charging object 131 and the secondelectrode 122, and a grounding unit 150 configured to intermittentlyinterconnect the second charging object 132 and a charge reservoir 171.

First and second substrates 110 and 120 are spaced apart from each otherby a certain distance. For example, the first substrate 110 may be anupper substrate, and the second substrate 120 may be a lower substrate.Each of the first and second substrates 110 and 120 may have a flatstructure, but is not limited thereto.

Each of the first and second substrates 110 and 120 may include a hardmaterial, e.g., a silicon wafer or glass. However, each of the first andsecond substrates 110 and 120 is not limited thereto and may include avariety of materials. For example, each of the first and secondsubstrates 110 and 120 may include a flexible material such as polyester(PE), polyethersulfone (PES), polyethylene naphthalate (PEN), or Kapton.

The first electrode 112 is provided on a bottom surface of the firstsubstrate 110, and the second electrode 122 is provided on a top surfaceof the second substrate 120. Each of the first and second electrodes 112and 122 may include a material having an excellent electricalconductivity. For example, each of the first and second electrodes 112and 122 may include at least one of graphene, carbon nanotubes (CNT),indium tin oxide (ITO), metal, and conductive polymer. Herein, the metalmay include at least one of, for example, silver (Ag), aluminum (Al),copper (Cu), gold (Au), nickel (Ni), chromium (Cr), and platinum (Pt),but is not limited thereto. Each of the first and second electrodes 112and 122 may have a monolayer structure or a multilayer structure.

The first charging object 131 is provided on a bottom surface of thefirst electrode 112 facing the second electrode 122, and may be apositively charged object. Herein, the first charging object 131 isprovided to contact the bottom surface of the first electrode 112. Thefirst charging object 131 is positively charged due to contact with thesecond charging object 132, and may include a material having a lowerelectrical conductivity compared to the second charging object 132. Forexample, the first charging object 131 may include a dielectric materialor an insulating material such as polyformaldehyde, ethylcellulose,polyamide, melamine formol, wool, silk, mica, or nylon. However, thefirst charging object 131 is not limited thereto and may include avariety of materials configured to (or capable of) being positivelycharged due to contact with the second charging object 132.

The second charging object 132 is provided between the first chargingobject 131 and the second electrode 122, and may be a negatively chargedobject. Herein, the second charging object 132 may be provided to bespaced apart from the first charging object 131 and the second electrode122 when no external force is applied to the triboelectric generator100.

The second charging object 132 is negatively charged due to contact withthe first charging object 131, and may include a conductive materialhaving a higher electrical conductivity compared to the first chargingobject 131 in order to facilitate charge transfer between the secondcharging object 132 and the charge reservoir 171 as will be describedbelow. The second charging object 132 may include a metallic materialsuch as Al, Cu, Ag, Au, or steel. However, the second charging object132 is not limited thereto and may include a variety of conductivematerials configured to (or capable of) being negatively charged due tocontact with the first charging object 131.

For example, the first and second charging objects 131 and 132 may bemade of nylon and Al, or mica and Au, respectively. However, theabove-mentioned combinations of materials are merely examples and thefirst and second charging objects 131 and 132 may be made of variouscombinations of materials.

At least one of the first and second charging objects 131 and 132 may bedoped with a p-type dopant or an n-type dopant to control surface chargecharacteristics thereof. A source of the p-type dopant may include, forexample, an ionic liquid such as NO₂BF₄, NOBF₄, or NO₂SbF₆, an acidiccompound such as HCl, H₂PO₄, CH₃COOH, H₂SO₄, or HNO₃, or an organiccompound such as dichlorodicyanoquinone (DDQ), Oxone,dimyristoylphosphatidylinositol (DMPI), or trifluoromethanesulfonimide.Otherwise, the source of the p-type dopant may include HPtCl₄, AuCl₃,HAuCl₄, silver trifluoromethanesulfonate (AgOTf), AgNO₃, H₂PdCl₆,Pd(OAc)₂, or Cu(CN)₂.

A source of the n-type dopant may include, for example, a reductionproduct of a substituted or unsubstituted nicotinamide, a reductionproduct of a compound which is chemically bound to a substituted orunsubstituted nicotinamide, or a compound comprising at least twopyridinium moieties in which a nitrogen atom of at least one of thepyridinium moieties is reduced. For example, the source of the n-typedopant may include nicotinamide mononucleotide-H (NMNH), nicotinamideadenine dinucleotide-H (NADH), nicotinamide adenine dinucleotidephosphate-H (NADPH), or viologen. Otherwise, the source of the n-typedopant may include polymer such as polyethylenimine (PEI).Alternatively, the n-type dopant may include alkali metal such aspotassium (K) or lithium (Li). The above-mentioned materials of thep-type and n-type dopants are merely examples, and a variety of othermaterials may be used as the dopants.

The grounding unit 150 is provided to intermittently contact the secondcharging object 132 due to motion of the second charging object 132. Thegrounding unit 150 is electrically connected to the charge reservoir171. Herein, the charge reservoir 171 may be, for example, the ground.Accordingly, the grounding unit 150 may intermittently interconnect thesecond charging object 132 and the charge reservoir 171 due to motion ofthe second charging object 132.

The grounding unit 150 may be provided between the second chargingobject 132 and the second substrate 120 to be intermittently connectedto the second charging object 132 due to motion of the second chargingobject 132. In this regard, the grounding unit 150 may include aconductive member 151 configured to intermittently contact the secondcharging object 132 due to motion of the second charging object 132, andan elastic member 152 configured to elastically support motion of theconductive member 151. Herein, the conductive member 151 is electricallyconnected to the charge reservoir 171. The grounding unit 150 may beprovided on the second substrate 120 serving as a lower substrate, butis not limited thereto.

In the above-described configuration of the grounding unit 150, when thesecond charging object 132 moves toward the second electrode 122 andcontacts the conductive member 151 of the grounding unit 150, the secondcharging object 132 may be electrically connected to the chargereservoir 171. As such, electrons in the second charging object 132 maymove through the grounding unit 150 to the charge reservoir 171, orelectrons in the charge reservoir 171 may move through the groundingunit 150 to the second charging object 132. Otherwise, when the secondcharging object 132 moves away from the second electrode 122 and isseparated from the conductive member 151 of the grounding unit 150, thesecond charging object 132 may be insulated from the charge reservoir171.

One or more first elastic supporters 141 may be provided between thefirst substrate 110 and the second charging object 132, and one or moresecond elastic supporters 142 may be provided between the secondcharging object 132 and the second substrate 120. Herein, the first andsecond elastic supporters 141 and 142 may include, for example, firstand second springs, respectively. However, the first and second elasticsupporters 141 and 142 are not limited thereto and may include a varietyof other elastic members. FIG. 1 illustrates an example in which fourfirst springs are provided between the first substrate 110 and thesecond charging object 132 at corners thereof, and four second springsare provided between the second charging object 132 and the secondsubstrate 120 at corners thereof.

Each of the first elastic supporters 141 may have a modulus ofelasticity less than that of each of the second elastic supporters 142.For example, when the first and second elastic supporters 141 and 142are implemented as first and second springs, respectively, the firstsprings may have a spring constant less than that of the second springs.As such, when the first substrate 110 is pressed, the distance betweenthe first substrate 110 and the second charging object 132 is reducedand then the distance between the second charging object 132 and thesecond substrate 120 is reduced. Subsequently, the first and secondcharging objects 131 and 132 contact each other and then the secondcharging object 132 sequentially contact the conductive member 151 ofthe grounding unit 150 and the second electrode 122.

A description is now given of an operating mechanism of thetriboelectric generator 100 illustrated in FIGS. 1 and 2.

FIGS. 3A to 3H are cross-sectional views for describing a first cycleoperating mechanism of the triboelectric generator 100.

FIG. 3A illustrates a state when no external force is applied to thetriboelectric generator 100. In FIG. 3A, reference numeral 161 denotes afirst load for detecting the flow of electrons between the first andsecond electrodes 112 and 122, and reference numeral 162 denotes asecond load for detecting the flow of electrons between the groundingunit 150 and the charge reservoir 171.

FIG. 3B illustrates a state in which the first and second chargingobjects 131 and 132 contact each other. Referring to FIG. 3B, since eachof the first elastic supporters 141 has a modulus of elasticity lessthan that of each of the second elastic supporters 142 as describedabove, when a pressing force is applied to the first substrate 110,initially, the distance between the first substrate 110 and the secondcharging object 132 is reduced and thus the first and second chargingobjects 131 and 132 contact each other. Herein, as described above, thefirst and second charging objects 131 and 132 are positively andnegatively charged objects, respectively. Accordingly, when the firstand second charging objects 131 and 132 contact each other, a contactsurface of the first charging object 131 may be positively charged, anda contact surface of the second charging object 132 may be negativelycharged. Subsequently, when the pressing force is continuously appliedto the first substrate 110, as illustrated in FIG. 3C, the secondcharging object 132 moves toward the second electrode 122 while thefirst and second charging objects 131 and 132 contact each other.

FIG. 3D illustrates a state in which the second charging object 132contacts the grounding unit 150 while the first and second chargingobjects 131 and 132 contact each other. Referring to FIG. 3D, when thepressing force is continuously applied to the first substrate 110 whilethe first and second charging objects 131 and 132 contact each other,the second charging object 132 contacts the conductive member 151 of thegrounding unit 150. Herein, the conductive member 151 is electricallyconnected to the charge reservoir 171, e.g., the ground. In this state,since the first and second charging objects 131 and 132 achieve chargeequilibration therebetween, charge transfer does not occur between thesecond charging object 132 and the charge reservoir 171.

FIG. 3E illustrates a state in which the second charging object 132contacts the second electrode 122 while the first and second chargingobjects 131 and 132 contact each other. Referring to FIG. 3E, when thepressing force is continuously applied to the first substrate 110 whilethe second charging object 132 contacts the conductive member 151 of thegrounding unit 150, the second charging object 132 contacts the secondelectrode 122. Herein, the second charging object 132 constantlycontacts the conductive member 151 of the grounding unit 150. In thisstate, although the first and second charging objects 131 and 132contact each other and the second charging object 132 contacts thesecond electrode 122 and the conductive member 151 of the grounding unit150, since charge equilibration is achieved, charge transfer does notoccur between the second charging object 132 and the charge reservoir171.

FIG. 3F illustrates a state in which the second charging object 132 andthe second electrode 122 are separated from each other and the first andsecond charging objects 131 and 132 are separated from each other.Referring to FIG. 3F, when the force applied to the first substrate 110is released, the second charging object 132 is separated from the secondelectrode 122, and the first charging object 131 is separated from thesecond charging object 132. Herein, the second charging object 132constantly contacts the conductive member 151 of the grounding unit 150.In this state, electrons move from the second charging object 132, whichis a negatively charged object, to the charge reservoir 171 to achievecharge equilibration in the second charging object 132, and thus acurrent flows through the second load 162. In addition, positive chargesin a surface of the first charging object 131, which is a positivelycharged object, induce negative charges in the first electrode 112,which is an upper electrode. As such, electrons move from the secondelectrode 122 to the first electrode 112 and thus a current flowsthrough the first load 161.

When the force applied to the first substrate 110 is continuouslyreleased, the second charging object 132 is separated from theconductive member 151 of the grounding unit 150 as illustrated in FIG.3G, and then the triboelectric generator 100 returns to an initial statethereof as illustrated in FIG. 3H. In the state of FIG. 3H, the firstand second electrodes 112 and 122 are maintained in negatively andpositively charged states, respectively, and the first charging object131 is maintained in a positively charged state. Positive and negativecharges in the second charging object 132 move an thus the secondcharging object 132 is maintained in a neutral state.

FIGS. 4A to 4H are cross-sectional views for describing a second cycleoperating mechanism of the triboelectric generator 100.

FIG. 4A illustrates the same state as FIG. 3H, in which the first andsecond electrodes 112 and 122 are maintained in negatively andpositively charged states, respectively, the first charging object 131is maintained in a positively charged state, and the second chargingobject 132 is maintained in a neutral state.

FIG. 4B illustrates a state in which the first and second chargingobjects 131 and 132 contact each other. Referring to FIG. 4B, when apressing force is applied to the first substrate 110, initially, thedistance between the first substrate 110 and the second charging object132 is reduced and thus the first and second charging objects 131 and132 contact each other. When the positively charged first chargingobject 131 contacts the second charging object 132 including aconductive material as described above, a contact surface (e.g., a topsurface) of the second charging object 132 is negatively charged, and asurface (e.g., a bottom surface) opposite to the contact surface of thesecond charging object 132 is positively charged.

FIG. 4C illustrates a state in which electrostatic induction occursbetween the second charging object 132 and the second electrode 122.Referring to FIG. 4C, when the pressing force is continuously applied tothe first substrate 110, the second charging object 132 approaches thesecond electrode 122 while the first and second charging objects 131 and132 contact each other. In the above-described state in which the secondcharging object 132 and the second electrode 122 are close to eachother, positive charges in the bottom surface of the second chargingobject 132 induce negative charges in the second electrode 122 due toelectrostatic induction. As such, electrons move from the firstelectrode 112 to the second electrode 122 and thus a current flowsthrough the first load 161.

FIG. 4D illustrates a state in which the second charging object 132contacts the grounding unit 150 while the first and second chargingobjects 131 and 132 contact each other. Referring to FIG. 4D, when thepressing force is continuously applied to the first substrate 110 whilethe first and second charging objects 131 and 132 contact each other,the second charging object 132 contacts the conductive member 151 of thegrounding unit 150. Herein, the conductive member 151 is electricallyconnected to the charge reservoir 171. In this state, electrons movefrom the charge reservoir 171 to the second charging object 132 toachieve charge equilibration among the first electrode 112, the firstcharging object 131, the second charging object 132, and the secondelectrode 122, and thus a current flows through the second load 162.

FIG. 4E illustrates a state in which the second charging object 132contacts the second electrode 122 while the first and second chargingobjects 131 and 132 contact each other. Referring to FIG. 4E, when thepressing force is continuously applied to the first substrate 110 whilethe second charging object 132 contacts the conductive member 151 of thegrounding unit 150, the second charging object 132 contacts the secondelectrode 122. Herein, the second charging object 132 constantlycontacts the conductive member 151 of the grounding unit 150. In thisstate, although the first and second charging objects 131 and 132contact each other and the second charging object 132 contacts thesecond electrode 122 and the conductive member 151 of the grounding unit150, since charge equilibration is achieved, charge transfer does notoccur between the second charging object 132 and the charge reservoir171.

FIG. 4F illustrates a state in which the second charging object 132 andthe second electrode 122 are separated from each other and the first andsecond charging objects 131 and 132 are separated from each other.Referring to FIG. 4F, when the force applied to the first substrate 110is released, the second charging object 132 is separated from the secondelectrode 122, and the first charging object 131 is separated from thesecond charging object 132. Herein, the second charging object 132constantly contacts the conductive member 151 of the grounding unit 150.In this state, electrons move from the second charging object 132, whichis a negatively charged object, to the charge reservoir 171 to achievecharge equilibration in the second charging object 132, and thus acurrent flows through the second load 162. In addition, positive chargesin a surface of the first charging object 131, which is a positivelycharged object, induce negative charges in the first electrode 112,which is an upper electrode. As such, electrons move from the secondelectrode 122 to the first electrode 112 and thus a current flowsthrough the first load 161.

When the force applied to the first substrate 110 is continuouslyreleased, the second charging object 132 is separated from theconductive member 151 of the grounding unit 150 as illustrated in FIG.4G, and then the triboelectric generator 100 returns to an initial statethereof as illustrated in FIG. 4H. Like the state of FIG. 4A, in thestate of FIG. 4H, the first and second electrodes 112 and 122 aremaintained in negatively and positively charged states, respectively,and the first charging object 131 is maintained in a positively chargedstate. Positive and negative charges in the second charging object 132move an thus the second charging object 132 is maintained in a neutralstate. Thereafter, when a pressing force is applied again to the firstsubstrate 110, the triboelectric generator 100 repeats theabove-described second cycle operation.

As described above, in the triboelectric generator 100 according to someexample embodiments, electrical energy may be generated between thefirst and second electrodes 112 and 122 and between the second chargingobject 132 and the charge reservoir 171 by pressing the first substrate110. Accordingly, when an external force is repeatedly applied to thetriboelectric generator 100, electrical energy may be efficientlyobtained.

FIG. 5 is a cross-sectional view of a modified example of the secondcharging object 132 of the triboelectric generator 100 illustrated inFIG. 1. Referring to FIG. 5, a plurality of protrusions 132 a may beprovided on a contact surface of the second charging object 132contacting the first charging object 131. Herein, the protrusions 132 amay have, for example, a wire shape or a pyramid shape, but are notlimited thereto. When the protrusions 132 a are provided on the contactsurface of the second charging object 132 as described above, an areacontacting the first charging object 131 may be increased and thuselectrical energy may be more efficiently obtained. Although FIG. 5illustrates an example in which the protrusions 132 a are provided onthe contact surface of the second charging object 132, the protrusions132 a are not limited thereto and may be provided on a contact surfaceof the first charging object 131 or on the contact surfaces of both thefirst and second charging objects 131 and 132.

FIG. 6 is a cross-sectional view of a charge reservoir 172 of atriboelectric generator 100 a modified from FIG. 1. Referring to FIG. 6,the charge reservoir 172 may be electrically connected to the conductivemember 151 of the grounding unit 150, and may include a conductivemember such as a metal film. FIG. 6 illustrates an example in which theconductive member configured as the charge reservoir 172 has a plateshape and is provided below the second substrate 120. However, theconductive member is not limited thereto and may have a variety ofshapes and positions.

FIG. 7 is a cross-sectional view of a grounding unit 180 of atriboelectric generator 100 b modified from FIG. 1. Referring to FIG. 7,the grounding unit 180 may include a switching device configured tointermittently interconnect the second charging object 132 and thecharge reservoir 171. The switching device may include, for example, amechanical switch or a solid-state switch (e.g., complementarymetal-oxide semiconductor (CMOS) device), but is not limited thereto.The switching device may electrically connect or insulate the secondcharging object 132 and the charge reservoir 171 to or from each otherunder certain conditions. For example, when the triboelectric generator100 b regularly operates, the switching device may establish and releaseelectrical connection between the second charging object 132 and thecharge reservoir 171 in a preset cycle. Alternatively, the switchingdevice may establish and release electrical connection between thesecond charging object 132 and the charge reservoir 171 by receivingvoltage and/or current information of the first and second electrodes112 and 122.

FIG. 8 is a cross-sectional view of a grounding unit 190 of atriboelectric generator 100 c modified from FIG. 1. Referring to FIG. 8,the grounding unit 190 may include a conductive member 191 configured toelectrically connect the second charging object 132 and the chargereservoir 171 to each other, and an insulating member 192 configured toelectrically insulate the second charging object 132 and the chargereservoir 171 from each other. For example, the grounding unit 190 maybe provided at an edge between the first and second substrates 110 and120, and may include the conductive member 191 fixed to the firstsubstrate 110, and the insulating member 192 extending downward from theconductive member 191. Herein, due to motion of the first substrate 110,the conductive member 191 may electrically connect the second chargingobject 132 and the charge reservoir 171 to each other, and theinsulating member 192 may electrically insulate the second chargingobject 132 and the charge reservoir 171 from each other.

FIGS. 9A to 9C are cross-sectional views showing operation of thegrounding unit 190 illustrated in FIG. 8.

Referring to FIG. 9A, when a pressing force is applied to the firstsubstrate 110 and thus the first substrate 110 moves downward, the firstand second charging objects 131 and 132 contact each other. In thisprocess, the second charging object 132 may be constantly electricallyinsulated from the charge reservoir 171 by the insulating member 192 ofthe grounding unit 150. Referring to FIG. 9B, when the first substrate110 continuously moves downward, the second charging object 132 may beelectrically connected to the charge reservoir 171 by the conductivemember 191 of the grounding unit 190 while the first and second chargingobjects 131 and 132 contact each other. Referring to FIG. 9C, when thefirst substrate 110 continuously moves downward, the second chargingobject 132 may contact the second electrode 122 while the secondcharging object 132 is electrically connected to the charge reservoir171. As described above, electrical connection between the secondcharging object 132 and the charge reservoir 171 may be established andreleased using the conductive member 191 and the insulating member 192of the grounding unit 190.

FIG. 10 is a cross-sectional view of a triboelectric generator 200according to some example embodiments. Except that first and secondcharging objects 231 and 232 are negatively and positively chargedobjects, respectively, the triboelectric generator 200 illustrated inFIG. 10 is the same as the triboelectric generator 100 illustrated inFIGS. 1 and 2. The following description is focused on differences fromFIGS. 1 and 2.

Referring to FIG. 10, the triboelectric generator 200 includes first andsecond electrodes 212 and 222, a first charging object 231 provided on asurface of the first electrode 212, a second charging object 232provided between the first charging object 231 and the second electrode222, and a grounding unit 250 configured to intermittently interconnectthe second charging object 232 and a charge reservoir 271.

First and second substrates 210 and 220 are spaced apart from each otherby a certain distance. Each of the first and second substrates 210 and220 may include a hard material or a flexible material. The firstelectrode 212 is provided on a bottom surface of the first substrate210, and the second electrode 222 is provided on a top surface of thesecond substrate 220. Each of the first and second electrodes 212 and222 may include a material having an excellent electrical conductivity.For example, the first and second electrodes 212 and 222 may include atleast one of graphene, CNT, ITO, metal, and conductive polymer. Each ofthe first and second electrodes 212 and 222 may have a monolayerstructure or a multilayer structure.

The first charging object 231 is provided on a bottom surface of thefirst electrode 212 facing the second electrode 222, and may be anegatively charged object. Herein, the first charging object 231 isprovided to contact the bottom surface of the first electrode 212. Thefirst charging object 231 is negatively charged due to contact with thesecond charging object 232 to be described below, and may include amaterial having a low electrical conductivity. For example, the firstcharging object 231 may include polytetrafluoroethylene (Teflon),polydimethylsiloxane (PDMS), polyvinyl chloride (PVC), polyimide(Kapton), polypropylene (PP), polyethylene (PE), or polystyrene (PS).However, the first charging object 231 is not limited thereto and mayinclude a variety of materials configured to (or capable of) beingnegatively charged due to contact with the second charging object 232.

The second charging object 232 is provided between the first chargingobject 231 and the second electrode 222, and may be a positively chargedobject. Herein, the second charging object 232 may be provided to bespaced apart from the first charging object 231 and the second electrode222 when no external force is applied to the triboelectric generator200.

The second charging object 232 is positively charged due to contact withthe first charging object 231, and may include a conductive materialhaving a high electrical conductivity in order to facilitate chargetransfer between the second charging object 232 and the charge reservoir271. The second charging object 232 may include, for example, Al, Cu,Ag, Au, or steel. However, the second charging object 232 is not limitedthereto and may include a variety of conductive materials configured to(or capable of) being positively charged due to contact with the firstcharging object 231. As described above, at least one of the first andsecond charging objects 231 and 232 may be doped with a p-type dopant oran n-type dopant to control surface charge characteristics thereof.

The grounding unit 250 is provided to intermittently contact the secondcharging object 232 due to motion of the second charging object 232. Thegrounding unit 250 is electrically connected to the charge reservoir271. Herein, the charge reservoir 271 may be, for example, the ground.Accordingly, the grounding unit 250 may intermittently interconnect thesecond charging object 232 and the charge reservoir 271 due to motion ofthe second charging object 232.

The grounding unit 250 may be provided between the second chargingobject 232 and the second substrate 220 to be intermittently connectedto the second charging object 232 due to motion of the second chargingobject 232. In this regard, the grounding unit 250 may include aconductive member 251 configured to intermittently contact the secondcharging object 232 due to motion of the second charging object 232, andan elastic member 252 configured to elastically support motion of theconductive member 251. Herein, the conductive member 251 is electricallyconnected to the charge reservoir 271.

One or more first elastic supporters 241 may be provided between thefirst substrate 210 and the second charging object 232, and one or moresecond elastic supporters 242 may be provided between the secondcharging object 232 and the second substrate 220. Each of the firstelastic supporters 241 may have a modulus of elasticity less than thatof each of the second elastic supporters 242.

A description is now given of an operating mechanism of thetriboelectric generator 200 illustrated in FIG. 10.

FIGS. 11A to 11H are cross-sectional views for describing a first cycleoperating mechanism of the triboelectric generator 200.

FIG. 11A illustrates a state when no external force is applied to thetriboelectric generator 200. In FIG. 11A, reference numeral 261 denotesa first load for detecting the flow of electrons between the first andsecond electrodes 212 and 222, and reference numeral 262 denotes asecond load for detecting the flow of electrons between the groundingunit 250 and the charge reservoir 271.

FIG. 11B illustrates a state in which the first and second chargingobjects 231 and 232 contact each other. Referring to FIG. 11B, when apressing force is applied to the first substrate 210, initially, thefirst and second charging objects 231 and 232 contact each other.Herein, since the first and second charging objects 231 and 232 arenegatively and positively charged objects, respectively, a contactsurface of the first charging object 231 may be negatively charged, anda contact surface of the second charging object 232 may be positivelycharged. Subsequently, when the pressing force is continuously appliedto the first substrate 210, as illustrated in FIG. 11C, the secondcharging object 232 moves toward the second electrode 222 while thefirst and second charging objects 231 and 232 contact each other.

FIG. 11D illustrates a state in which the second charging object 232contacts the grounding unit 250 while the first and second chargingobjects 231 and 232 contact each other. Referring to FIG. 11D, when thepressing force is continuously applied to the first substrate 210 whilethe first and second charging objects 231 and 232 contact each other,the second charging object 232 contacts the conductive member 251 of thegrounding unit 250. Herein, the conductive member 251 is electricallyconnected to the charge reservoir 271, e.g., the ground. In this state,since the first and second charging objects 231 and 232 achieve chargeequilibration therebetween, charge transfer does not occur between thesecond charging object 232 and the charge reservoir 271.

FIG. 11E illustrates a state in which the second charging object 232contacts the second electrode 222 while the first and second chargingobjects 231 and 232 contact each other. Referring to FIG. 11E, when thepressing force is continuously applied to the first substrate 210 whilethe second charging object 232 contacts the conductive member 251 of thegrounding unit 250, the second charging object 232 contacts the secondelectrode 222. Herein, the second charging object 232 constantlycontacts the conductive member 251 of the grounding unit 250. In thisstate, although the first and second charging objects 231 and 232contact each other and the second charging object 232 contacts thesecond electrode 222 and the conductive member 251 of the grounding unit250, since charge equilibration is achieved, charge transfer does notoccur between the second charging object 232 and the charge reservoir271.

FIG. 11F illustrates a state in which the second charging object 232 andthe second electrode 222 are separated from each other and the first andsecond charging objects 231 and 232 are separated from each other.Referring to FIG. 11F, when the force applied to the first substrate 210is released, the second charging object 232 is separated from the secondelectrode 222, and the first charging object 231 is separated from thesecond charging object 232. Herein, the second charging object 232constantly contacts the conductive member 251 of the grounding unit 250.In this state, electrons move from the charge reservoir 271 to thesecond charging object 232, which is a positively charged object, toachieve charge equilibration in the second charging object 232, and thusa current flows through the second load 262. In addition, negativecharges in a surface of the first charging object 231, which is anegatively charged object, induce positive charges in the firstelectrode 212, which is an upper electrode. As such, electrons move fromthe first electrode 212 to the second electrode 222 and thus a currentflows through the first load 261.

When the force applied to the first substrate 210 is continuouslyreleased, the second charging object 232 is separated from theconductive member 251 of the grounding unit 250 as illustrated in FIG.11G, and then the triboelectric generator 200 returns to an initialstate thereof as illustrated in FIG. 11H. In the state of FIG. 11H, thefirst and second electrodes 212 and 222 are maintained in positively andnegatively charged states, respectively, and the first charging object231 is maintained in a negatively charged state. Positive and negativecharges in the second charging object 232 move an thus the secondcharging object 232 is maintained in a neutral state.

FIGS. 12A to 12H are cross-sectional views for describing a second cycleoperating mechanism of the triboelectric generator 200.

FIG. 12A illustrates the same state as FIG. 11H, in which the first andsecond electrodes 212 and 222 are maintained in positively andnegatively charged states, respectively, the first charging object 231is maintained in a negatively charged state, and the second chargingobject 232 is maintained in a neutral state.

FIG. 12B illustrates a state in which the first and second chargingobjects 231 and 232 contact each other. Referring to FIG. 12B, when apressing force is applied to the first substrate 210, initially, thedistance between the first substrate 210 and the second charging object232 is reduced and thus the first and second charging objects 231 and232 contact each other. When the negatively charged first chargingobject 231 contacts the second charging object 232 including aconductive material as described above, a contact surface (e.g., a topsurface) of the second charging object 232 is positively charged, and asurface (e.g., a bottom surface) opposite to the contact surface of thesecond charging object 232 is negatively charged.

FIG. 12C illustrates a state in which electrostatic induction occursbetween the second charging object 232 and the second electrode 222.Referring to FIG. 12C, when the pressing force is continuously appliedto the first substrate 210, the second charging object 232 approachesthe second electrode 222 while the first and second charging objects 231and 232 contact each other. In the above-described state in which thesecond charging object 232 and the second electrode 222 are close toeach other, negative charges in the bottom surface of the secondcharging object 232 induce positive charges in the second electrode 222due to electrostatic induction. As such, electrons move from the secondelectrode 222 to the first electrode 212 and thus a current flowsthrough the first load 261.

FIG. 12D illustrates a state in which the second charging object 232contacts the grounding unit 250 while the first and second chargingobjects 231 and 232 contact each other. Referring to FIG. 12D, when thepressing force is continuously applied to the first substrate 210 whilethe first and second charging objects 231 and 232 contact each other,the second charging object 232 contacts the conductive member 251 of thegrounding unit 250. In this state, electrons move from the secondcharging object 232 to the charge reservoir 271 to achieve chargeequilibration among the first electrode 212, the first charging object231, the second charging object 232, and the second electrode 222, andthus a current flows through the second load 262.

FIG. 12E illustrates a state in which the second charging object 232contacts the second electrode 222 while the first and second chargingobjects 231 and 232 contact each other. Referring to FIG. 12E, when thepressing force is continuously applied to the first substrate 210 whilethe second charging object 232 contacts the conductive member 251 of thegrounding unit 250, the second charging object 232 contacts the secondelectrode 222. Herein, the second charging object 232 constantlycontacts the conductive member 251 of the grounding unit 250. In thisstate, although the first and second charging objects 231 and 232contact each other and the second charging object 232 contacts thesecond electrode 222 and the conductive member 251 of the grounding unit250, since charge equilibration is achieved, charge transfer does notoccur between the second charging object 232 and the charge reservoir271.

FIG. 12F illustrates a state in which the second charging object 232 andthe second electrode 222 are separated from each other and the first andsecond charging objects 231 and 232 are separated from each other.Referring to FIG. 12F, when the force applied to the first substrate 210is released, the second charging object 232 is separated from the secondelectrode 222, and the first charging object 231 is separated from thesecond charging object 232. Herein, the second charging object 232constantly contacts the conductive member 251 of the grounding unit 250.In this state, electrons move from the charge reservoir 271 to thesecond charging object 232, which is a positively charged object, toachieve charge equilibration in the second charging object 232, and thusa current flows through the second load 262. In addition, negativecharges in a surface of the first charging object 231, which is anegatively charged object, induce positive charges in the firstelectrode 212, which is an upper electrode. As such, electrons move fromthe first electrode 212 to the second electrode 222 and thus a currentflows through the first load 261.

When the force applied to the first substrate 210 is continuouslyreleased, the second charging object 232 is separated from theconductive member 251 of the grounding unit 250 as illustrated in FIG.12G, and then the triboelectric generator 200 returns to an initialstate thereof as illustrated in FIG. 12H. Like the state of FIG. 12A, inthe state of FIG. 12H, the first and second electrodes 212 and 222 aremaintained in positively and negatively charged states, respectively,and the first charging object 231 is maintained in a negatively chargedstate. Positive and negative charges in the second charging object 232move an thus the second charging object 232 is maintained in a neutralstate. Thereafter, when a pressing force is applied again to the firstsubstrate 210, the triboelectric generator 200 repeats theabove-described second cycle operation.

As described above, in the triboelectric generator 200 according to someexample embodiments, electrical energy may be generated between thefirst and second electrodes 212 and 222 and between the second chargingobject 232 and the charge reservoir 271 by pressing the first substrate210. Accordingly, when an external force is repeatedly applied to thetriboelectric generator 200, electrical energy may be efficientlyobtained.

As described above, a plurality of protrusions may be provided on atleast one of the contact surfaces of the first and second chargingobjects 231 and 232. The charge reservoir 271 may include a conductivemember instead of the ground. The grounding unit 250 may include aswitching device configured to establish or release electricalconnection between the second charging object 232 and the chargereservoir 271. Alternatively, the grounding unit 250 may include aconductive member configured to electrically connect the second chargingobject 232 and the charge reservoir 271 to each other, and an insulatingmember configured to electrically insulate the second charging object232 and the charge reservoir 271 from each other.

FIG. 13 is a perspective view of a triboelectric generator 300 accordingto some example embodiments.

Referring to FIG. 13, the triboelectric generator 300 includes first andsecond substrates 310 and 320, first and second electrodes 312 and 322,a first charging object 331 provided on a surface of the first electrode312, a second charging object 332 provided between the first chargingobject 331 and the second electrode 322, and a grounding unit 350configured to intermittently interconnect the second charging object 332and a charge reservoir 371. The triboelectric generator 300 has aphysical structure or mechanism in which the first charging object 331,the second charging object 332, and the second electrode 322 are spacedapart and separated from each other when no external force is appliedthereto, and contact each other when an external force is appliedthereto.

Each of the first and second substrates 310 and 320 may include amaterial having flexibility to be transformed due to an external forceand having a restoring force to return to an original state thereof whenthe external force is removed. For example, each of the first and secondsubstrates 310 and 320 may include polyester (PE), polyethersulfone(PES), polyethylene naphthalate (PEN), or Kapton, but is not limitedthereto. The first and second substrates 310 and 320 are provided toface each other with respect to the second charging object 332intervening therebetween. For example, the first substrate 310 may havea convex shape in an upward direction from the second charging object332, and the second substrate 320 may have a convex shape in a downwarddirection from the second charging object 332. Herein, the firstsubstrate 310 may include a material configured to (or capable of) beingmore easily transformed compared to the second substrate 320 in such amanner that the first substrate 310 is initially transformed when anexternal force is applied to the triboelectric generator 300.

The first electrode 312 is provided on a bottom surface of the firstsubstrate 310, and the second electrode 322 is provided on a top surfaceof the second substrate 320. The first and second electrodes 312 and 322may have flexibility corresponding to transformation of the first andsecond substrates 310 and 320. Each of the first and second electrodes312 and 322 may include a material having an excellent electricalconductivity. For example, each of the first and second electrodes 312and 322 may include at least one of graphene, CNT, ITO, metal, andconductive polymer. Herein, the metal may include at least one of, forexample, Ag, Al, Cu, Au, Ni, Cr, and Pt, but is not limited thereto.Each of the first and second electrodes 312 and 322 may have a monolayerstructure or a multilayer structure.

The first charging object 331 is provided on a bottom surface of thefirst electrode 312 facing the second electrode 322. The second chargingobject 332 is provided between the first charging object 331 and thesecond electrode 322. The first and second charging objects 331 and 332may have flexibility corresponding to transformation of the first andsecond substrates 310 and 320. Herein, the first charging object 331 isprovided to contact the bottom surface of the first electrode 312. Thesecond charging object 332 is provided to be spaced apart from the firstcharging object 331 and the second electrode 322 when no external forceis applied to the triboelectric generator 300. The first and secondcharging objects 331 and 332 may include materials to be charged withopposite polarities due to contact therebetween.

The first and second charging objects 331 and 332 may be positively andnegatively charged objects, respectively. In this case, the firstcharging object 331 is positively charged due to contact with the secondcharging object 332, and may include a material having a low electricalconductivity. For example, the first charging object 331 may includepolyformaldehyde, ethylcellulose, polyamide, melamine formol, wool,silk, mica, or nylon, but is not limited thereto. The second chargingobject 332 is negatively charged due to contact with the first chargingobject 331, and may include a conductive material having a highelectrical conductivity in order to facilitate charge transfer betweenthe second charging object 332 and the charge reservoir 371. The secondcharging object 332 may include, for example, Al, Cu, Ag, Au, or steel.However, the second charging object 332 is not limited thereto.

Alternatively, the first and second charging objects 331 and 332 may benegatively and positively charged objects, respectively. In this case,the first charging object 331 is negatively charged due to contact withthe second charging object 332, and may include a material having a lowelectrical conductivity. For example, the first charging object 331 mayinclude polytetrafluoroethylene (Teflon), polydimethylsiloxane (PDMS),polyvinyl chloride (PVC), polyimide (Kapton), polypropylene (PP),polyethylene (PE), or polystyrene (PS), but is not limited thereto. Thesecond charging object 332 is positively charged due to contact with thefirst charging object 331, and may include a conductive material havinga high electrical conductivity in order to facilitate charge transferbetween the second charging object 332 and the charge reservoir 371. Thesecond charging object 332 may include, for example, Al, Cu, Ag, Au, orsteel, but is not limited thereto.

As described above, at least one of the first and second chargingobjects 331 and 332 may be doped with a p-type dopant or an n-typedopant to control surface charge characteristics thereof.

The grounding unit 350 is provided to intermittently interconnect thesecond charging object 332 and the charge reservoir 371. Herein, thecharge reservoir 371 may be, for example, the ground or a conductivemember. As such, the grounding unit 350 may intermittently interconnectthe second charging object 332 and the charge reservoir 371 due tomotion of the second charging object 332. Specifically, when the secondcharging object 332 moves toward the second electrode 322 and contactsthe grounding unit 350, the second charging object 332 may beelectrically connected to the charge reservoir 371. Otherwise, when thesecond charging object 332 moves away from the second electrode 322 andis separated from the grounding unit 350, the second charging object 332may be insulated from the charge reservoir 371. Examples of thegrounding unit 350 configured to (or capable of) implementing theabove-described function have been described above, and thus a detaileddescription of the grounding unit 350 is not provided herein.

FIGS. 14A to 14E are cross-sectional views showing operation of thetriboelectric generator 300 illustrated in FIG. 13.

FIG. 14A illustrates an initial state of the triboelectric generator 300before being transformed. As illustrated in FIG. 14B, when a pressingforce is applied to the first substrate 310, initially, at least a partof the first substrate 310, which is an upper substrate, moves and istransformed toward the second charging object 332. In this process, thefirst charging object 331 may contact the second charging object 332.

Referring to FIG. 14C, when the first substrate 310 is continuouslypressed, the second charging object 332 moves and is transformed towardthe second electrode 322 while the first and second charging objects 331and 332 contact each other. In this process, the second charging object332 may contact the grounding unit 350. Subsequently, referring to FIG.14D, when the first substrate 310 is further pressed, the secondcharging object 332 contacts the second electrode 322 while the firstand second charging objects 331 and 332 contact each other. In thisstate, the second charging object 332 constantly contacts the groundingunit 350.

Then, referring to FIG. 14E, when the force applied to the firstsubstrate 310 is released, the second charging object 332 is separatedfrom the second electrode 322, and the first charging object 331 isseparated from the second charging object 332. When the force applied tothe first substrate 310 is continuously released, the triboelectricgenerator 300 returns to the initial state thereof as illustrated inFIG. 14A.

A mechanism of generating electrical energy due to the above-describedoperation of the triboelectric generator 300 has been described indetail above, and thus a description thereof is not provided herein. Aplurality of protrusions may be provided on at least one of the contactsurfaces of the first and second charging objects 331 and 332.Electrical energy may be efficiently obtained using a flexible materialfor the triboelectric generator 300.

FIG. 15 is a cross-sectional view of a triboelectric generator 400according to some example embodiments.

Referring to FIG. 15, the triboelectric generator 400 includes first andsecond substrates 410 and 420, first and second electrodes 412 and 422,a first charging object 431 provided on a surface of the first electrode412, a second charging object 432 provided between the first chargingobject 431 and the second electrode 422, and a grounding unit 450configured to intermittently interconnect the second charging object 432and a charge reservoir 471. First supporters 441 are provided betweenthe first substrate 410 and the second charging object 432, and secondsupporters 442 are provided between the second charging object 432 andthe second substrate 420.

Each of the first and second substrates 410 and 420 may include amaterial having flexibility to be transformed due to an external forceand having stretchability to extend or contract. The first electrode 412is provided on a bottom surface of the first substrate 410, and thesecond electrode 422 is provided on a top surface of the secondsubstrate 420. The first and second electrodes 412 and 422 may haveflexibility and stretchability corresponding to the first and secondsubstrates 410 and 420. Each of the first and second electrodes 412 and422 may include a material having an excellent electrical conductivity.

The first charging object 431 is provided on a bottom surface of thefirst electrode 412 facing the second electrode 422. The second chargingobject 432 is provided between the first charging object 431 and thesecond electrode 422. The first and second charging objects 431 and 432may have flexibility and stretchability corresponding to the first andsecond substrates 410 and 420. Herein, the first charging object 431 isprovided to contact the bottom surface of the first electrode 412. Thesecond charging object 432 is provided to be spaced apart from the firstcharging object 431 and the second electrode 422 when no external forceis applied to the triboelectric generator 400. Herein, the first andsecond charging objects 431 and 432 may include materials to be chargedwith opposite polarities due to contact therebetween.

The first and second charging objects 431 and 432 may be positively andnegatively charged objects, respectively. In this case, the firstcharging object 431 is positively charged due to contact with the secondcharging object 432, and may include a material having a low electricalconductivity. The second charging object 432 is negatively charged dueto contact with the first charging object 431, and may include aconductive material having a high electrical conductivity.Alternatively, the first and second charging objects 431 and 432 may benegatively and positively charged objects, respectively. In this case,the first charging object 431 is negatively charged due to contact withthe second charging object 432, and may include a material having a lowelectrical conductivity. The second charging object 432 is positivelycharged due to contact with the first charging object 431, and mayinclude a conductive material having a high electrical conductivity. Asdescribed above, at least one of the first and second charging objects431 and 432 may be doped with a p-type dopant or an n-type dopant tocontrol surface charge characteristics thereof.

The grounding unit 450 is provided to intermittently interconnect thesecond charging object 432 and the charge reservoir 471. Herein, thecharge reservoir 471 may be, for example, the ground or a conductivemember. As such, the grounding unit 450 may intermittently interconnectthe second charging object 432 and the charge reservoir 471 due tomotion of the second charging object 432. Specifically, when the secondcharging object 432 moves toward the second electrode 422 and contactsthe grounding unit 450, the second charging object 432 may beelectrically connected to the charge reservoir 471. Otherwise, when thesecond charging object 432 moves away from the second electrode 422 andis separated from the grounding unit 450, the second charging object 432may be insulated from the charge reservoir 471. Examples of thegrounding unit 450 configured to (or capable of) implementing theabove-described function have been described above, and thus a detaileddescription of the grounding unit 450 is not provided herein.

The first supporters 441 may be provided at two edges between the firstsubstrate 410 and the second charging object 432. The second supporters442 may be provided at two edges between the second charging object 432and the second substrate 420. Each of the first and second supporters441 and 442 may include a hard material not to be easily transformed dueto an external force.

FIGS. 16A to 16D are cross-sectional views showing operation of thetriboelectric generator 400 illustrated in FIG. 15.

As illustrated in FIG. 16A, when a pressing force is applied to thefirst substrate 410, at least a part of the first substrate 410, whichis an upper substrate, extends and is transformed toward the secondcharging object 432. In this process, the first charging object 431 maycontact the second charging object 432. Referring to FIG. 16B, when thefirst substrate 410 is continuously pressed, the second charging object432 extends, is transformed, and moves toward the second electrode 422while the first and second charging objects 431 and 432 contact eachother. In this process, the second charging object 432 may contact thegrounding unit 450.

Referring to FIG. 16C, when the first substrate 410 is further pressed,the second charging object 432 further extends, is transformed, andcontacts the second electrode 422 while the first and second chargingobjects 431 and 432 contact each other. In this state, the secondcharging object 432 constantly contacts the grounding unit 450. Then, asillustrated in FIG. 16D, when the force applied to the first substrate410 is released, the second charging object 432 is separated from thesecond electrode 422, and the first charging object 431 is separatedfrom the second charging object 432. When the force applied to the firstsubstrate 410 is continuously released, the triboelectric generator 400returns to an initial state thereof in which no external force isapplied thereto.

A mechanism of generating electrical energy due to the above-describedoperation of the triboelectric generator 400 has been described indetail above, and thus a description thereof is not provided herein. Asdescribed above, a plurality of protrusions may be provided on at leastone of the contact surfaces of the first and second charging objects 431and 432. Electrical energy may be efficiently obtained using a flexibleand stretchable material for the triboelectric generator 400.

FIG. 17 is a cross-sectional view of a triboelectric generator 500according to some example embodiments.

Referring to FIG. 17, the triboelectric generator 500 includes first andsecond substrates 510 and 520, first and second electrodes 512 and 522,a first charging object 531 provided on a surface of the first electrode512, a second charging object 532 provided between the first chargingobject 531 and the second electrode 522, and a grounding unit 550configured to intermittently interconnect the second charging object 532and a charge reservoir 571. A first supporter 541 is provided betweenthe first substrate 510 and the second charging object 532, and a secondsupporter 542 is provided between the second charging object 532 and thesecond substrate 520.

Each of the first and second substrates 510 and 520 may include amaterial having flexibility to be transformed due to an external forceand having stretchability to extend or contract. The first electrode 512is provided on a bottom surface of the first substrate 510, and thesecond electrode 522 is provided on a top surface of the secondsubstrate 520. The first and second electrodes 512 and 522 may haveflexibility and stretchability corresponding to the first and secondsubstrates 510 and 520. Each of the first and second electrodes 512 and522 may include a material having an excellent electrical conductivity.

The first charging object 531 is provided on a bottom surface of thefirst electrode 512 facing the second electrode 522. The second chargingobject 532 is provided between the first charging object 531 and thesecond electrode 522. The first and second charging objects 531 and 532may have flexibility and stretchability corresponding to the first andsecond substrates 510 and 520. Herein, the first charging object 531 isprovided to contact the bottom surface of the first electrode 512. Thesecond charging object 532 is provided to be spaced apart from the firstcharging object 531 and the second electrode 522 when no external forceis applied to the triboelectric generator 500. Herein, the first andsecond charging objects 531 and 532 may include materials to be chargedwith opposite polarities due to contact therebetween.

The first and second charging objects 531 and 532 may be positively andnegatively charged objects, respectively. In this case, the firstcharging object 531 is positively charged due to contact with the secondcharging object 532, and may include a material having a low electricalconductivity. The second charging object 532 is negatively charged dueto contact with the first charging object 531, and may include aconductive material having a high electrical conductivity.Alternatively, the first and second charging objects 531 and 532 may benegatively and positively charged objects, respectively. In this case,the first charging object 531 is negatively charged due to contact withthe second charging object 532, and may include a material having a lowelectrical conductivity. The second charging object 532 is positivelycharged due to contact with the first charging object 531, and mayinclude a conductive material having a high electrical conductivity. Asdescribed above, at least one of the first and second charging objects531 and 532 may be doped with a p-type dopant or an n-type dopant tocontrol surface charge characteristics thereof.

The grounding unit 550 is provided to intermittently interconnect thesecond charging object 532 and the charge reservoir 571. Herein, thecharge reservoir 571 may be, for example, the ground or a conductivemember. As such, the grounding unit 550 may intermittently interconnectthe second charging object 532 and the charge reservoir 571 due tomotion of the second charging object 532. Specifically, when the secondcharging object 532 moves toward the second electrode 522 and contactsthe grounding unit 550, the second charging object 532 may beelectrically connected to the charge reservoir 571. Otherwise, when thesecond charging object 532 moves away from the second electrode 522 andis separated from the grounding unit 550, the second charging object 532may be insulated from the charge reservoir 571. Examples of thegrounding unit 550 configured to (or capable of) implementing theabove-described function have been described above, and thus a detaileddescription of the grounding unit 550 is not provided herein.

The first supporter 541 may be provided at an edge between the firstsubstrate 510 and the second charging object 532, and the secondsupporter 542 may be provided at an edge between the second chargingobject 532 and the second substrate 520. Herein, the first supporter 541may be located above the second supporter 542. Each of the first andsecond supporters 541 and 542 may include a hard material not to beeasily transformed due to an external force.

FIGS. 18A to 18D are cross-sectional views showing operation of thetriboelectric generator 500 illustrated in FIG. 17.

As illustrated in FIG. 18A, when a pressing force is applied to an endof the first substrate 510 not supported by the first and secondsupporters 541 and 542, the first substrate 510 extends, is transformed,and moves toward the second charging object 532. In this process, thefirst charging object 531 may contact the second charging object 532.Referring to FIG. 18B, when the end of the first substrate 510 iscontinuously pressed, an end of the second charging object 532 extends,is transformed, and moves toward the second electrode 522 while thefirst and second charging objects 531 and 532 contact each other. Inthis process, the second charging object 532 may contact the groundingunit 550.

Referring to FIG. 18C, when the end of the first substrate 510 isfurther pressed, the second charging object 532 further extends, istransformed, and contacts the second electrode 522 while the first andsecond charging objects 531 and 532 contact each other. In this state,the second charging object 532 constantly contacts the grounding unit550. Then, as illustrated in FIG. 18D, when the force applied to thefirst substrate 510 is released, the second charging object 532 isseparated from the second electrode 522, and the first charging object531 is separated from the second charging object 532. When the forceapplied to the first substrate 510 is continuously released, thetriboelectric generator 500 returns to an initial state thereof in whichno external force is applied thereto.

A mechanism of generating electrical energy due to the above-describedoperation of the triboelectric generator 500 has been described indetail above, and thus a description thereof is not provided herein. Asdescribed above, a plurality of protrusions may be provided on at leastone of the contact surfaces of the first and second charging objects 531and 532.

FIG. 19 is a cross-sectional view of a triboelectric generator 600according to some example embodiments.

Referring to FIG. 19, the triboelectric generator 600 includes first andsecond substrates 610 and 620, first and second electrodes 612 and 622,a first charging object 631 provided on a surface of the first electrode612, a second charging object 632 provided between the first chargingobject 631 and the second electrode 622, and a grounding unit 650configured to intermittently interconnect the second charging object 632and a charge reservoir 671.

The first substrate 610 may have a spherical shape, and the secondsubstrate 620 may have a spherical shape surrounding the first substrate610. The first electrode 612 is provided on an outer surface of thefirst substrate 610, and the second electrode 622 is provided on aninner surface of the second substrate 620. Each of the first and secondelectrodes 612 and 622 may include a material having an excellentelectrical conductivity.

The first charging object 631 is provided on an outer surface of thefirst electrode 612, and the second charging object 632 is providedbetween the first charging object 631 and the second electrode 622.Herein, the first charging object 631 is provided to contact the outersurface of the first electrode 612, and the second charging object 632is provided to be spaced apart from the first charging object 631 andthe second electrode 622 when no external force is applied to thetriboelectric generator 600. The first and second charging objects 631and 632 may include materials to be charged with opposite polarities dueto contact therebetween.

The first and second charging objects 631 and 632 may be positively andnegatively charged objects, respectively. In this case, the firstcharging object 631 is positively charged due to contact with the secondcharging object 632, and may include a material having a low electricalconductivity. The second charging object 632 is negatively charged dueto contact with the first charging object 631, and may include aconductive material having a high electrical conductivity.Alternatively, the first and second charging objects 631 and 632 may benegatively and positively charged objects, respectively. In this case,the first charging object 631 is negatively charged due to contact withthe second charging object 632, and may include a material having a lowelectrical conductivity. The second charging object 632 is positivelycharged due to contact with the first charging object 631, and mayinclude a conductive material having a high electrical conductivity. Asdescribed above, at least one of the first and second charging objects631 and 632 may be doped with a p-type dopant or an n-type dopant tocontrol surface charge characteristics thereof.

An elastic supporter 640 is provided between the first and secondcharging objects 631 and 632. The elastic supporter 640 may be, forexample, a spring provided between the first and second charging objects631 and 632, but is not limited thereto. FIG. 19 illustrates an examplein which the elastic supporter 640 is provided on the first chargingobject 631. A string 660 is connected to the first charging object 631and is provided to penetrate through the second charging object 632, thesecond electrode 622, and the second substrate 620 and to be exposedoutside. FIG. 19 illustrates an example in which the string 660 isprovided under the first charging object 631.

The grounding unit 650 is provided to intermittently interconnect thesecond charging object 632 and the charge reservoir 671. Herein, thecharge reservoir 671 may be, for example, the ground or a conductivemember. As such, the grounding unit 650 may intermittently interconnectthe second charging object 632 and the charge reservoir 671 due tomotion of the second charging object 632. Specifically, when the secondcharging object 632 moves toward the second electrode 622 and contactsthe grounding unit 650, the second charging object 632 may beelectrically connected to the charge reservoir 671. Otherwise, when thesecond charging object 632 moves away from the second electrode 622 andis separated from the grounding unit 650, the second charging object 632may be insulated from the charge reservoir 671. Examples of thegrounding unit 650 configured to (or capable of) implementing theabove-described function have been described above, and thus a detaileddescription of the grounding unit 650 is not provided herein.

FIGS. 20A to 20D are cross-sectional views showing operation of thetriboelectric generator 600 illustrated in FIG. 19.

As illustrated in FIG. 20A, when the string 660 is pulled downward, thefirst substrate 610, the first electrode 612, and the first chargingobject 631 move downward. In this process, the first charging object 631may contact the second charging object 632. Referring to FIG. 20B, whenthe string 660 is continuously pulled, the second charging object 632moves toward the second electrode 622 while the first and secondcharging objects 631 and 632 contact each other. In this process, thesecond charging object 632 may contact the grounding unit 650.

Referring to FIG. 20C, when the string 660 is further pulled, the secondcharging object 632 moves downward and contacts the second electrode 622while the first and second charging objects 631 and 632 contact eachother. In this state, the second charging object 632 constantly contactsthe grounding unit 650. Then, as illustrated in FIG. 20D, when the forceapplied to the string 660 is released, the second charging object 632 isseparated from the second electrode 622, and the first charging object631 is separated from the second charging object 632. When the forceapplied to the string 660 is continuously released, the triboelectricgenerator 600 returns to an initial state thereof in which no externalforce is applied thereto.

A mechanism of generating electrical energy due to the above-describedoperation of the triboelectric generator 600 has been described indetail above, and thus a description thereof is not provided herein. Asdescribed above, a plurality of protrusions may be provided on at leastone of the contact surfaces of the first and second charging objects 631and 632.

FIG. 21 is a cross-sectional view of a triboelectric generator 700according to some example embodiments.

Referring to FIG. 21, the triboelectric generator 700 includes first andsecond substrates 710 and 720, first and second electrodes 712 and 722,a first charging object 731 provided on a surface of the first electrode712, a second charging object 732 provided between the first chargingobject 731 and the second electrode 722, and a grounding unit 750configured to intermittently interconnect the second charging object 732and a charge reservoir 771. Each of the first and second substrates 710and 720 may have a flat structure and include a hard material or aflexible material. The first electrode 712 is provided on a bottomsurface of the first substrate 710, and the second electrode 722 isprovided on a top surface of the second substrate 720. Each of the firstand second electrodes 712 and 722 may include a material having anexcellent electrical conductivity.

The first charging object 731 is provided on a bottom surface of thefirst electrode 712, and the second charging object 732 is providedbetween the first charging object 731 and the second electrode 722.Herein, the first charging object 731 is provided to contact the bottomsurface of the first electrode 712. The second charging object 732 isprovided to be spaced apart from the first charging object 731 and thesecond electrode 722 when no external force is applied to thetriboelectric generator 700. Herein, the first and second chargingobjects 731 and 732 may include materials to be charged with oppositepolarities due to contact therebetween.

The first and second charging objects 731 and 732 may be positively andnegatively charged objects, respectively. In this case, the firstcharging object 731 is positively charged due to contact with the secondcharging object 732, and may include a material having a low electricalconductivity. The second charging object 732 is negatively charged dueto contact with the first charging object 731, and may include aconductive material having a high electrical conductivity.Alternatively, the first and second charging objects 731 and 732 may benegatively and positively charged objects, respectively. In this case,the first charging object 731 is negatively charged due to contact withthe second charging object 732, and may include a material having a lowelectrical conductivity. The second charging object 732 is positivelycharged due to contact with the first charging object 731, and mayinclude a conductive material having a high electrical conductivity. Asdescribed above, at least one of the first and second charging objects731 and 732 may be doped with a p-type dopant or an n-type dopant tocontrol surface charge characteristics thereof.

The grounding unit 750 is provided to intermittently interconnect thesecond charging object 732 and the charge reservoir 771. Herein, thecharge reservoir 771 may be, for example, the ground or a conductivemember. As such, the grounding unit 750 may intermittently interconnectthe second charging object 732 and the charge reservoir 771 due tomotion of the second charging object 732. Specifically, when the secondcharging object 732 moves toward the second electrode 722 and contactsthe grounding unit 750, the second charging object 732 may beelectrically connected to the charge reservoir 771. Otherwise, when thesecond charging object 732 moves away from the second electrode 722 andis separated from the grounding unit 750, the second charging object 732may be insulated from the charge reservoir 771. Examples of thegrounding unit 750 configured to (or capable of) implementing theabove-described function have been described above, and thus a detaileddescription of the grounding unit 750 is not provided herein.

Guide members 790 configured to guide vertical motion of the firstsubstrate 710, the first electrode 712, and the first charging object731 may be provided on a top surface of the second charging object 732.The guide members 790 may be provided at two edges on the secondcharging object 732. Elastic supporters 740 may be provided between thesecond charging object 732 and the second substrate 720. The elasticsupporters 740 may be provided at two edges between the second chargingobject 732 and the second substrate 720.

FIGS. 22A to 22D are cross-sectional views showing operation of thetriboelectric generator 700 illustrated in FIG. 21.

As illustrated in FIG. 22A, when a pressing force is applied to thefirst substrate 710, the first substrate 710 moves toward the secondcharging object 732. In this process, the first charging object 731 maycontact the second charging object 732. Referring to FIG. 22B, when thefirst substrate 710 is continuously pressed, the second charging object732 moves toward the second electrode 722 while the first and secondcharging objects 731 and 732 contact each other. In this process, thesecond charging object 732 may contact the grounding unit 750.

Referring to FIG. 22C, when the first substrate 710 is further pressed,the second charging object 732 contacts the second electrode 722 whilethe first and second charging objects 731 and 732 contact each other. Inthis state, the second charging object 732 constantly contacts thegrounding unit 750. Then, as illustrated in FIG. 22D, when the forceapplied to the first substrate 710 is released, the second chargingobject 732 is separated from the second electrode 722, and the firstcharging object 731 is separated from the second charging object 732.When the force applied to the first substrate 710 is continuouslyreleased, the triboelectric generator 700 returns to an initial statethereof in which no external force is applied thereto.

A mechanism of generating electrical energy due to the above-describedoperation of the triboelectric generator 700 has been described indetail above, and thus a description thereof is not provided herein. Aplurality of protrusions may be provided on at least one of the contactsurfaces of the first and second charging objects 731 and 732.

FIG. 23 is a cross-sectional view of a triboelectric generator accordingto some example embodiments.

Referring to FIG. 23, the triboelectric generator 700′ may be the sameas the triboelectric generator 700 illustrated in FIG. 21, except thetriboelectric generator 700′ may further include one or more elasticsupporters 741 provided between the first charging object 731 and thesecond charging object 732.

FIGS. 24A to 24D are cross-sectional views showing operation of thetriboelectric generator illustrated in FIG. 23. The operation of thetriboelectric generator 700′ in FIGS. 24A to 24D may be the same as (orsubstantially the same as) the operation of the triboelectric generator700 in FIGS. 22A to 22D.

Referring to FIG. 24A, when a pressing force sufficient to compress theelastic supporters 741 is applied to the first substrate 710, the firstsubstrate 710 moves toward the second charging object 732. In thisprocess, the first charging object 731 may contact the second chargingobject 732, and the elastic supporters 741 may be compressed. Referringto FIG. 24B, when the first substrate 710 is continuously pressed, thesecond charging object 732 moves toward the second electrode 722 whilethe first and second charging objects 731 and 732 contact each other. Inthis process, the second charging object 732 may contact the groundingunit 750.

Referring to FIG. 24C, when the first substrate 710 is further pressed,the second charging object 732 contacts the second electrode 722 whilethe first and second charging objects 731 and 732 contact each other. Inthis state, the second charging object 732 constantly contacts thegrounding unit 750. Then, as illustrated in FIG. 24D, when the forceapplied to the first substrate 710 is released, the elastic supporters741 may return to their non-compressed state, and the triboelectricgenerator 700′ returns to an initial state thereof in which no externalforce is applied thereto.

FIG. 25 is a cross-sectional view of a triboelectric generator accordingto some example embodiments.

Referring to FIG. 25, the triboelectric generator 700″ may be the sameas the triboelectric generator 700 illustrated in FIG. 21, except thetriboelectric generator 700″ may further include one or more firstmagnets M1 attached to a surface of the first charging object 731 and/orone or more second magnets M2 attached to a surface of the secondcharging object 732. As shown in FIG. 25, the first magnet M1 may be ona surface of the first charging object 731 that faces the secondcharging object 732. The second magnet M2 may be on a surface of thesecond charging object 732 that faces the first charging object 731. Thefirst magnet M1 and the second magnet M2 may repel each other. Thus, therepulsive force of the first magnet M1 and the second magnet M2 may keepthe first charging object 731 and the second charging object 732separated from each other unless a pressing force greater than therepulsive force of the first magnet M1 and the second magnet M2 isapplied to the first substrate 110.

The operation of the triboelectric generator 700″ may be the same as orsimilar to operation of the triboelectric generators 700 and 700′described in FIGS. 22A to 22D and 24A to 24D.

FIG. 26 is an illustration of a triboelectric system according to someexample embodiments.

Referring to FIG. 26, a triboelectric system 1000 may include aplurality of tiles T spaced apart from each other in an array or otherpattern. Each tile T may include a plurality of triboelectric generators100 (or any type of the triboelectric generators described above)electrically connected to each other and embedded in the tiles T.Vibrations caused by environment factors (e.g., sound, persons walkingon the tiles) may provide pressing forces to the triboelectricgenerators embedded in the tiles T for generating electricity using theembedded triboelectric generators 100.

As described above, a triboelectric generator configured to (or capableof) efficiently obtaining electrical energy may be implemented bypreparing two charging objects to be charged with opposite polaritiesdue to contact therebetween, and intermittently connecting one of thecharging objects via a grounding unit to a charge reservoir, e.g., theground.

It should be understood that example embodiments described herein shouldbe considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within eachtriboelectric generator according to example embodiment should typicallybe considered as available for other similar features or aspects inother triboelectric generators according to example embodiments.

While some example embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope as defined by the following claims.

What is claimed is:
 1. A triboelectric generator comprising: first andsecond electrodes spaced apart from each other; a first charging objectand a second charging object, the first charging object being on asurface of the first electrode facing the second electrode, the firstcharging object configured to be positively charged due to contact withthe second charging object, the second charging object being between thefirst charging object and the second electrode, the second chargingobject configured to be negatively charged due to contact with the firstcharging object; and a grounding unit configured to intermittentlyinterconnect the second charging object and a charge reservoir due tomotion of the second charging object, wherein the first charging objectcontacts the surface of the first electrode, and the second chargingobject is configured to be spaced apart from the first charging objectand the second electrode.
 2. The triboelectric generator of claim 1,wherein, the first and second charging objects are configured contacteach other in response to a first force being applied to at least one ofthe first and second electrodes, the second charging object and thesecond electrode are configured to contact each other in response to asecond force being applied to the at least one of the first and secondelectrodes, and the second force is more than the first force.
 3. Thetriboelectric generator of claim 2, wherein the second charging objectis configured to electrically connect to the charge reservoir via thegrounding unit in response to the second charging object moving towardsthe second electrode.
 4. The triboelectric generator of claim furthercomprising: first elastic supporters connected to a first surface of thesecond charging object; and second elastic supporters connected to asecond surface of the second charging object that is opposite the firstsurface and faces the second electrode.
 5. The triboelectric generatorof claim 4, wherein each of the first elastic supporters has a modulusof elasticity that is less than a modulus of elasticity of each of thesecond elastic supporters.
 6. The triboelectric generator of claim 1,wherein the first charging object includes at least one ofpolyformaldehyde, ethylcellulose, polyamide, melamine formol, wool,silk, mica, and nylon.
 7. The triboelectric generator of claim 1,wherein the second charging object includes a conductive material. 8.The triboelectric generator of claim 7, wherein the second chargingobject includes at least one of aluminum (Al), copper (Cu), silver (Ag),gold (Au), and steel.
 9. The triboelectric generator of claim 1, whereinat least one of the first and second charging objects includes a dopantto control charge characteristics thereof.
 10. The triboelectricgenerator of claim 1, wherein at least one of a contact surface of thefirst charging object and a contact surface of the second chargingobject include a plurality of protrusions.
 11. The triboelectricgenerator of claim 1, wherein each of the first and second electrodesinclude at least one of graphene, carbon nanotubes (CNT), indium tinoxide (ITO), metal, and conductive polymer.
 12. The triboelectricgenerator of claim 1, wherein the first and second electrodes are onfirst and second substrates, respectively.
 13. The triboelectricgenerator of claim 12, wherein each of the first and second substratesinclude one of a hard material and a flexible material.
 14. Thetriboelectric generator of claim 1, wherein the grounding unit includesa conductive member and an elastic member, the conductive member isbetween the second charging object and the second electrode, theconductive member is configured to intermittently contact the secondcharging object, and the elastic member is configured to elasticallysupport the conductive member.
 15. The triboelectric generator of claim1, wherein the grounding unit includes a switching device configured tointermittently interconnect the second charging object and the chargereservoir.
 16. The triboelectric generator of claim 1, wherein thegrounding unit includes a conductive member and an insulating member,the conductive member is configured to electrically connect the secondcharging object and the charge reservoir to each other, and theinsulating member is configured to insulate the second charging objectand the charge reservoir from each other.
 17. The triboelectricgenerator of claim 1, wherein the charge reservoir includes one of aground and a conductive member.
 18. The triboelectric generator of claim17, wherein the conductive member includes a metal film.